Root Division: Multiply Your Medicinal Herb Harvest with These Plant Propagation Tips
Written and Photographed by Juliet Blankespoor
Division is the easiest form of vegetative propagation. It involves digging up and severing a portion of the root system of a plant, and replanting it. Depending on the plant species and age, one to twenty divisions may be made from one plant. In running plants, such as the mints (Mentha spp.), partridgeberry (Mitchella repens), gotu kola (Centella asiatica), jiaogulan (Gynostemma pentaphyllum), Monarda spp., and Arnica chamissonis, one digs up the runners (stolons and rhizomes) and plants them in a new site or container. In clumping plants, such as elecampane (Inula helenium), valerian (Valeriana officinalis), Echinacea spp., motherwort (Leonurus cardiaca), meadowsweet (Filipendula ulmaria), boneset (Eupatorium perfoliatum), comfrey (Symphytum spp.), and culver’s root (Veronicastrum virginicum), one can thrust a shovel into the center of the clump and pry free the divisionling. I generally don’t have the heart for this method and prefer digging up the whole plant and getting a good look at its root system. I then divide the roots with a garden knife (hori-hori), shovel, or pruners and replant each section in it’s new garden spot. Each section contains either buds (when the plant is dormant) or leaves and shoots if the plant is actively growing and green. Take care to plant your divisionlings with the buds pointing up.
August 2021 Safety Update: Boneset and comfrey contain pyrrolizidine alkaloids (PAs), which can be harmful to the liver over time when ingested internally. Recent research shows that the PAs found in these plants (and other PA-containing plants) can be taken up by other plants when grown in close proximity or when comfrey is used in the garden as mulch or fertilizer. In light of this, we are recommending that comfrey should not be interplanted with herbs or food plants in the garden that will be ingested or used as mulch or fertilizer to err on the side of caution. However, mature compost that includes comfrey does not seem to contain PAs once it has been fully composted according to this study.
In the two images above, a clump of calamus (Acorus calamus) is divided. The image on the bottom shows three pieces that are ready to be transplanted to a new home in the garden.
Most people divide plants in the fall or spring when the plant is dormant and the temperatures are not too cold. I prefer to make divisions in the fall as there is generally less garden work than the springtime, and the roots may also grow when the plant is dormant. With my nursery, I have planted small roots from division in the fall and come spring, peeked into the pot and witnessed the growth of a larger root system, all taking place in the absence of photosynthesis! Early spring is also a fine time to divide plants. If you have a leafy active plant, cut back some of the growth as the inevitable damage to the root system will stress the plant with more leaves transpiring and losing moisture. Water in your divisionlings; seaweed tea will encourage root growth, which will increase their survival. Depending on the season, species, size of division, expertise, loving care in the transition to plant independence (watering, soil, etc.) you might have 70-100% survival.
Lucky for herbalists, early spring and fall are also the best times to harvest roots! If you’ve got your sights set on harvesting the roots of clump- or rhizome-forming medicinals, you can take part of the plant for medicine and replant the rest.
In the four images below, a clump of meadowsweet is dug up, and pulled apart into smaller pieces which are then ready for transplanting in the garden (or in our case, into nursery pots).
We replant our divisionlings in pots with our nursery. Consider hosting or attending a spring seed/plant swap; it's a great way to get to know other plant folks, learn about new useful plants, and increase variety in the garden without purchasing plants.
This article is an excerpt from a larger article on plant propagation.
Meet The Green Mastermind Behind Blog Castanea:
JULIET BLANKESPOOR founded the Chestnut School of Herbal Medicine in 2007 and serves as the school’s primary instructor and Creative Director. She's been a professional plant-human matchmaker for close to three decades. Juliet caught the plant bug when she was nineteen and went on to earn a degree in Botany. She's owned just about every type of herbal business you can imagine: an herbal nursery, a medicinal products business, a clinical practice, and now, an herbal school.
These days, she channels her botanical obsession with her writing and photography in her online programs and here on her personal blog, Castanea. She's writing her first book: Cultivating Medicinal Herbs: Grow, Harvest, and Prepare Handcrafted Remedies from Your Home Garden. Juliet and her houseplants share a home with her family and herb books in Asheville, North Carolina.
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